A microelectronic package comprises a microelectronic die electrically interconnected with a carrier substrate, and one or more other components, such as electrical interconnects, an integrated heat spreader, a heat sink, among others. An example of a microelectronic package is an integrated circuit microprocessor. A microelectronic die comprises a plurality of interconnected microcircuits within a carrier to perform electronic circuit functions.
A microelectronic die generates heat as a result of the electrical activity of the microcircuits. In order to minimize the damaging effects of heat, passive and active thermal management devices are used. Such thermal management devices include heat sinks, heat spreaders, and fans, among many others. There are limitations in the use of each type of device, and in many cases, the thermal management device is specifically designed for a particular microelectronic die and package design and intended operation. Examples of passive thermal management devices include heat sinks and integrated heat spreaders. Examples of active thermal management devices include package-based liquid cooling system including a micro-channel cold plate (MCCP).
A conventional micro-channel cold plate (MCCP) is shown in FIGS. 1a and 1b. FIG. 1a shows a housing portion of a conventional MCCP from a top plan view, and FIG. 1b shows a cross-sectional view of the MCCP taken along a length thereof and mounted on a package. It is noted at the outset that the MCCP shown in FIGS. 1a and 1b is not to scale. As shown in FIGS. 1a and 1b, a MCCP 115 according to the prior art may include a housing 102 defining a cooling fluid chamber 103, and having a die-side housing portion 104 and a cover plate portion 106. FIG. 1a shows a top plan view of the die-side housing portion 104. As seen in FIG. 1a, according to the prior art, the die-side housing portion 104 of a MCCP 115 may include a plurality of micro-channels 105 extending in a direction parallel to one another. The micro-channels 105 are adapted to direct cooling fluid from an inlet side 108 of the housing 102 to an outlet side 110 of the housing 102 as shown. Examples of cooling fluids include water, antifreeze such as potassium formate and K-formate, oil, liquid metal, low-melting-temperature solder alloy, nanofluid (that is, fluid with nano-particles), air and helium. The housing 102 may be made of silicon or copper, and the micro-channels 105 may be etched into the silicon or copper die-side housing portion 104 or provided using micro-machining techniques according to well-known methods. The cooling fluid is adapted to be delivered to the inlet side 108 of housing 102 by way of an inlet opening 112 in cover plate portion 106, and to exit the outlet side 110 through an outlet opening 114 in cover plate portion 106. The cooling fluid may be pumped through the MCCP 115 by a pump in a conventional closed loop cooling system. As shown in FIG. 1b, the MCCP 115 may be mounted onto a package 116 through thermal interface material (TIM) 118 as shown to form an MCCP-package assembly 100. TIM 118 may include a thermal interface pad or thermal grease, solder or epoxy. Package 116 as shown include a die 120 bonded to substrate 122 via electrically conductive and mechanically bonding joints 124 as shown. By “joint,” what is meant in the context of the instant description is a connection between the die and the substrate that is both electrically conductive and that further mechanically bonds the die to the substrate. Joints 124 are typically made of solder, and connect electrical contacts on the underside of the die 120 to corresponding electrical contacts on the substrate 122. Joints 124 as shown as encapsulated by a cured underfill material 126 as shown.
According to the prior art a MCCP 115 of which is depicted in FIGS. 1a and 1b, heat generated by the package 116 is dissipated at least in part through the MCCP 115 by circulating cooling fluid through micro-channels 105. The cooling fluid may be pumped through the cooling system by a pump and carried to a further heat sink device, such as, for example, a heat exchanger including fins, to dissipate heat energy from the cooing fluid 107 to the environment.
MCCP's according to the prior art disadvantageously require the use of lithographic and/or micro-machining techniques for providing the channels. Such techniques can be expensive, complicated and time-consuming to implement.
The prior art has as yet failed to provide a microelectronic die cooling device that is cost-effective, simple and efficient to fabricate.